The present invention relates to a pressure seal structure for sealing against a pressure difference between a fixed member and the surface of a movable member, and more particularly relates to a pressure seal structure for sealing against a pressure difference between a fixed member and the surface of a movable member, which is suitable for providing a pressure seal for the input or output side of a low pressure laminating machine such as a machine of a per se well known sort (for example, the machine disclosed in Japanese Patent Laying Open Publication No. 52-66581, or Japanese Patent Publication No. 53-31670) for laminating printed circuit boards at low pressure, when two such pressure seal structures are fitted so as to seal against two feed rollers of this laminating machine. The present invention also relates to a pressure sealed transfer mechanism comprising such a combination of two such pressure seal structures and two such feed or transfer rollers.
FIG. 1 is a sectional view of a prior art construction for inputing or feeding a sheet which is to be laminated into a low pressure laminating machine, for example of the sort disclosed in the above mentioned Japanese Patent Laying Open Publication No. 53-31670. In this figure, the reference numeral 1 denotes one of a pair of feed rollers, whose respective central rotational axes R and R' are parallel and extend in the plane perpendicular to the drawing paper, and the reference numeral 1' denotes the other of these feed rollers. These feed rollers 1 and 1' are typically rotatably supported at their extreme opposite portions in the directions perpendicular to the plane of the drawing paper in FIG. 1 by bearings or the like. Further, these feed rollers 1 and 1' are rotated respectively, as shown by the arrows denoted by the reference symbols b and b', in the clockwise and in the anticlockwise directions as seen in the drawing, and the feed roller 1 is in fairly tight contact with and pressed somewhat against the feed roller 1'. The feed rollers 1 and 1' are made of fairly resilient material, and thereby, as will be seen later, a fluid pressure seal is provided between their contact portions. A sheet 2, which is to be laminated by a low pressure laminating machine, and which may in some particular cases be a combination of sandwiched sheets which are to be laminated together, is directed to the feed rollers 1 and 1', being moved in the leftwards direction as shown by the arrow denoted by the reference symbol a in the drawing, so that its leading edge is entrapped, gripped, and fed by the feed rollers 1 and 1' in the leftwards direction as seen in the drawing.
The wall of the low pressure laminating machine into which the sheet 2 is to be fed is shown in section in FIG. 1, and is denoted by the reference numeral 3; the rest of this low pressure laminating machine is not shown, because its detailed structure is not relevant. This wall 3 is provided with a slot 8, through which the sheet 2 is required to pass, so that the sheet 2 can enter into the inside of the low pressure laminating machine. Thus, the slot 8 opposes the contact portions of the feed rollers 1 and 1'. As previously explained, the interior of the low pressure laminating machine is maintained at a low pressure, much lower than atmospheric pressure, and thus some form of sealing system is required to be provided, in order to stop atmospheric air from streaming in past the feed rollers 1 and 1' and through the slot 8, which would undesirably raise the pressure inside the laminating machine close to atmospheric pressure, thereby hampering or preventing proper lamination of the sheet 2 inside the laminating machine.
The prior art form of seal construction has been, as seen in FIG. 1, to insure that each of the feed rollers 1 and 1' to be in contact with and somewhat pressed against the wall 3 of the low pressure laminating machine, so as to form a pressure seal thereagainst, due to the above mentioned resilience of the feed rollers 1 and 1'. Further, as explained above, a pressure seal is provided between the contact portions of the feed rollers 1 and 1', because of the resilience of the feed rollers 1 and 1', both when no sheet 2 is being gripped by the feed rollers 1 and 1', as seen in FIG. 1, and also when a sheet 2 is being gripped by the feed rollers 1 and 1' and is being fed in the leftwards direction as seen in the figure through the slot 8 into the laminating machine. Thus, the space denoted in the figure by the symbol "S" located to the left in the drawing of the contact portions of the feed rollers 1 and 1' has been, in the above mentioned prior art, sealed against the entry of atmospheric air thereinto from the space at atmospheric pressure located to the right of the feed rollers 1 and 1' in the figure, and this sealing has ensured that large quantities of atmospheric air cannot enter through the slot 8 into the inside of the laminating machine, i.e. to the space on the left in the figure of the laminating machine wall 3.
However, this prior art form of construction for the input side of a low pressure laminating machine has encountered some problems, which mean that it is not really satisfactory.
In detail, the contact between the feed rollers 1 and 1' and the wall 3 of the laminating machine has tended to wear out both the wall 3 and also the feed rollers 1 and 1', because the material of the wall 3 is generally hard and not resilient. First, a consequence of this is that this wear may well cause deterioration of the sealing effect of the contact between the feed rollers 1 and 1' and the laminating machine wall 3, and also of the mutual contact between the feed rollers 1 and 1', due to irregularities on the feed rollers 1 and 1' and/or on the wall 3 caused by such wear. Second, another consequence is that detached pieces, principally of the feed rollers 1 and 1' which are generally softer and more liable to become destructively worn, but also of the wall 3, may adhere to the feed rollers 1 and 1' and may then be carried around by the rotation of the feed rollers 1 and 1', and may thus tend to be transferred to the surface of the sheet 2 which is being fed into the laminating machine. This is very troublesome, and can cause problems with regard to the quality of the laminated products such as printed circuit boards which are being made by the laminating machine, because such detached pieces can undesirably become sandwiched into the structure of these laminated products, after lamination thereof by the laminating machine. It should be noted that this particular problem is much less serious on the output side of a laminating machine, because there is no possiblity of such detached pieces of the output feed rollers becoming laminated into products produced by the laminating machine, when said detached pieces are deposited on the laminated products as they are being ejected from the laminating machine at the output side thereof.
This problem is aggravated by a particular result of the shown prior art construction, as follows. Because the feed rollers 1 and 1' are necessarily made of somewhat resilient material, as a matter of course they are somewhat flexible, even if reinforced. Now, the forces due to imbalance between the atmospheric pressure acting on the portions of the surfaces of the feed rollers 1 and 1' exposed thereto, and the low pressure inside the laminating machine acting on the portions of the surfaces of the feed rollers 1 and 1' exposed thereto, are very considerable, because as may be seen in the drawing major portions of the surfaces of these feed rollers 1 and 1' are exposed to the outside atmosphere, and also major portions of the surfaces of these feed rollers 1 and 1' are exposed to the low pressure inside the laminating machine. Accordingly, the forces due to the difference in these pressures are liable to cause some bending or bowing of the feed rollers 1 and 1', i.e. displacement of the central portions of the spans thereof, with regard to the extent of these feed rollers 1 and 1' in the direction perpendicular to the plane of the drawing paper in FIG. 1, respectively in the downwards and leftwards direction in FIG. 1, and in the upwards and leftwards direction therein. Any such bowing will cause the contact pressures between the feed rollers 1 and 1' and the wall 3 of the laminating machine to be sharply increased, especially at the above mentioned central parts of the spans of the feed rollers 1 and 1', i.e. at the parts of the feed rollers 1 and 1' where these feed rollers are not supported by bearings or the like. Of course, this uncontrolled increase in these contact pressures will cause a substantial increase in wear of the laminating machine wall 3 and also of the feed rollers 1 and 1', and thus will aggravate the above described problems of the prior art sealing system.